ABSTRACT

Objective:

In this study, the posterior and anterior axillary field dosimetries, where the target volume was determined on computerised tomography (CT), were compared in breast cancer irradiation.

Materials and Methods:

Twenty-six breast cancer patients were examined in this study. Target volumes were contoured by 2 physicians. The posterior field was established by traditional anatomical structures in the posterior axillary plan (PAP). The second anterior field was performed in the same gantry angle with Supraclacicular field (SCF) at the anterior axillary plan (AAP). V105 (volume receiving ≥105% prescribed dose), V80 ve V30 values, mean lung dose, V20 (lung volume receiving ≥20 Gy) value, maximum spinal cord dose, conformity index and monitor unit (MU) values were defined. Two independent groups were compared with Mann-Whitney U test, 2 dependent groups were compared with Wilcoxon’s signed rank test. p<0.05 was considered as statistically significant.

Results:

Small hot-point areas defined as volumes receiving more than 105% of the prescribed dose and more conformal 90% isodose curves were established at AAP. Low-dose areas were wider at PAP. Mean V105 (70.8 to 52.8, p=0.005), V80 and V30 volumes (p=0.005 and p=0.009 respectively), mean lung dose (p=0.04) and V20 value (p=0.03) were statistically significantly lower at AAP. There was no difference between two groups as maximum spinal cord dose. Conformity index was significantly higher at AAP (0.023 to 0.025, p=0.005). Treatment time was found longer at PAP (242.3 MU, p=0.047).

Conclusion:

According to the anatomy of the Turkish patients, AAP was superior when compared to the traditional method. The CT based treatment planning with dose optimization and target volume determination must be the standard treatment of SCF and axillary lymph node. Different techniques should be studied comparatively in terms of dosimetric and clinical superiority.